1. Field of the Invention
The present invention concerns an aperture stop device for use in a microscope, in particular in an operating microscope, with an adjustable magnification factor, a microscope, in particular an operating microscope, having a device for adjusting the magnification factor and an aperture stop device according to the invention and a method of adjusting an optical property of a microscope with an adjustable magnification factor.
2. Description of the Related Art
Microscopes and in particular stereoscopic operating microscopes have in the beam path behind the main objective a magnification changer with which different magnification factors can be implemented. The change in magnification can then be effected, while retaining the eyepiece, by changing the magnification factor by means of the magnification changer so that there is no need for a change in the eyepiece for altering the magnification. Zoom systems, also referred to as pancratic systems or vario-systems, or Galilean systems, are used as magnification changers. While a zoom system generally has a lens combination which is to be displaced in relationship relative to each other, a Galilean changer essentially includes a number of various lens combinations which are arranged fixedly relative to each other and which respectively correspond to the lens combination of a Galilean telescope and which can be moved alternately into the microscope beam path. Depending on which of the lens combinations is introduced into the microscope beam path, that then affords a different magnification factor. While a zoom system permits stepless adjustment of the magnification factor, only stepwise adjustment of the magnification factor is possible with a Galilean changer.
The aperture is of particular significance in terms of the resolution capability, light power and depth of focus of a microscope. The aperture is generally established by the orifice of an aperture stop or diaphragm which, when a magnification changer is provided, is connected downstream thereof in the microscope beam path.
A high light power and a high resolution capability require a large aperture, that is to say a large orifice in respect of the aperture stop, whereas a great depth of focus requires a small aperture, that is to say a small orifice in respect of the aperture stop. In order to increase the depth of focus the aperture must be reduced in size, which however results in a lower resolution capability and a lower level of light power for the microscope. If on the other hand the light power or the resolution capability respectively of the microscope is to be increased, then the aperture is to be enlarged, whereby the depth of focus of the microscope is reduced. A high level of light power and a high resolution capability are therefore linked to a low depth of focus and vice-versa.
It is possible for an iris aperture stop to be introduced into the beam path of a microscope. In the case of a stereoscopic operating microscope a so-called double iris aperture stop with a respective iris aperture stop is introduced into the partial beam paths. That iris or double iris aperture stop can be drawn open and closed mechanically so that the aperture which is made available by the aperture stop arrangement can be adjusted. When the aperture of the double iris aperture stop device, that is to say the diameter of the orifices of the irises, is adjusted, that establishes the transmission characteristic of a microscope, that is to say the proportion of the amount of radiation issuing from the microscope in relation to the amount of radiation passing into the microscope, as a function of the magnification factor. The light power characteristic, the resolution characteristic as well as the depth of focus characteristic, that is to say the light power, the level of resolution and the depth of focus respectively as a function of the respectively selected magnification factor, are also established with the transmission characteristic.
In comparison with that state of the art, an object of the present invention is to provide an aperture stop device which can be advantageously used in a microscope with an adjustable microscope parameter.
A further object of the present invention is to provide an improved microscope.
Finally, an object of the invention is to provide an advantageous method of adjusting an optical property of a microscope with an adjustable microscope parameter.